I tried to do sites_web_domain_add.
But I got this message
data_processing_errorpm_process_idle_timeout_error_regex<br /> pm_max_requests_error_regex<br /> SOAP Error: pm_process_idle_timeout_error_regex
pm_max_requests_error_regex.

This indicates that you did not pass the values for the variable pm_max_requests and pm_process_idle_timeout as part of the params array to the function. If you use a recent ispconfig version, then these values are required to be passed to the function as part of the params array.